How can I know if my safety switch don't work and need to replace?

First its not a good idea to piggyback your question on someone else's. This can lead to confusion. You should start a new thread. So I've moved your question to its own thread.

You need to provide more info here. Like make and model of car. Which safety switch you are referring to and what makes you think its not working.

P.S. We have no affiliation with Autozone.

Check the switch's continuity (ohms) with a multimeter.